This invention relates to procedures for tracking clinical laboratory measurements and calibrating measurement systems to ensure measurement reliability.
The Federal Clinical Laboratory Improvement Act (CLIA) requires that clinical laboratories run quality controls and participate in proficiency testing programs. CLIA has defined relatively wide tolerance limits for proficiency testing programs. Absolute set points are not defined for most controls, so most clinical laboratories establish their own set-point values based on the average of 15 to 20 measurements and track precision around these arbitrarily defined set points.
Most clinical laboratory measurements are performed with reagents and instruments that are manufactured by commercial companies. The processes used to manufacture these materials have multiple sources of variability, which result in final products that produce test measurements that differ both between instruments and within instruments across calibrations and across batches of reagents. Manufacturing processes for many laboratory measurement systems typically have tolerance limits of about xc2x110%. Efforts to reduce the tolerance limits typically are complex and increase the cost of manufacturing the measurement systems.
The median values for large distributions of patient test values are remarkably constant over time, assuming that the measurement systems and the patient demographics are relatively constant. Some laboratory measurements vary with pre-analytic variables such as food supplementation, and collection and transport conditions, but, if the number of measurements is large, most of these factors average out and do not cause major shifts in the distributions of test values. If specimens are collected from patients with characteristics different from the general population, such as, for example, patients from oncology, surgery, intensive care units, and pediatrics, the test distribution may change. When these differences are known, the test values can be mathematically adjusted to normalize the test distributions.
However, absent special circumstances, clinicians are seldom informed about changes in analytic bias or xe2x80x9cset-pointxe2x80x9d in clinical laboratory measurements, and their diagnostic processes cannot be readily adjusted to account for these level differences. Even if a laboratory is aware of a change in bias, there generally is no easy way to correct the problem unless the reagents and/or instruments used to make the clinical measurements are changed.
The combination of the wide control limits and arbitrarily set target values substantially reduces the value of un-assayed control materials in monitoring long-term analytic bias in a clinical laboratory. As a result, actual patient test values used in clinical decisions are not directly tracked, and their constancy is not controlled. These measurement variations may significantly impact treatment protocols in a patient population.
The present invention is directed to a method for more tightly controlling the distributions of analytic test values reported to clinicians by adjusting assay set points using a combination of traceable control materials and patient test values. The present invention also is directed to a computer readable medium encoded with a computer program arranged to execute such a method.
In one embodiment, the invention is a method for calibrating a clinical laboratory analytical instrument, including generating control pool data from a commutable control pool, wherein the control pools have target analyte values for an assay, generating patient specimen data from a distribution of test values from patient specimens; determining tolerance limits from the control pool data and the patient specimen data; and adjusting the calibration of the instrument with respect to the tolerance limits.
In a second embodiment, the invention provides a computer readable medium encoded with a computer program, the program being arranged such that, when the program is executed, a computer performs the acts of generating control pool data from a commutable control pool, wherein the control pools have target analyte values for an assay, generating patient specimen data from a distribution of test values from patient specimens; determining tolerance limits from the control pool data and the patient specimen data; and adjusting the calibration of the instrument with respect to the tolerance limits.
In a third embodiment, the invention is a chemical analyzer including a processor responsive to a computer program, the program being arranged such that, when the program is executed, the processor performs the acts of generating control pool data from a commutable control pool, wherein the control pools have target analyte values for an assay, generating patient specimen data from a distribution of test values from patient specimens; determining tolerance limits from the control pool data and the patient specimen data; and adjusting the calibration of the instrument with respect to the tolerance limits.
In a fourth embodiment, the invention is a clinical analytical instrumentation system including a central computer and a network of chemical analyzers, wherein at least one of the central computer and the analyzers includes a processor responsive to a computer program. The program is arranged such that, when the program is executed, the processor performs the acts of generating control pool data from a commutable control pool, wherein the control pools have target analyte values for an assay, generating patient specimen data from a distribution of test values from patient specimens, determining tolerance limits from the control pool data and the patient specimen data; and adjusting the calibration of the instrument with respect to the tolerance limits.
In a fifth embodiment, the invention is a method for analyzing data in an analytical laboratory, wherein the laboratory includes a central computer networked with at least one chemical analyzer. The method includes transferring assay data from the analyzers to the central computer, wherein a processor in the central computer generates control pool data from a commutable control pool, wherein the control pools have target analyte values for an assay, generates patient specimen data from a distribution of test values from patient specimens, determines tolerance limits from the control pool data and the patient specimen data; and adjusts the calibration of at least one chemical analyzer with respect to the tolerance limits.
The inventive method has the potential for markedly improving the clinical performance of automated laboratory measurement systems by both reducing the fluctuations in analytic bias and by anchoring these assays to traceable reference standards. If this procedure is accepted by the appropriate governing and licensure groups, (such as the U.S. Food and Drug Agency), it could provide a more cost-effective method for assay standardization. The tight industrial manufacturing processes required to assure equivalent levels of accuracy for an analytical laboratory instrument would generally be much more expensive than this method for calibration adjustment. The method of the invention has the added advantage of providing post-manufacturing confirmation of the performance of the measured systems in the medical center laboratories.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.